1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle with an engine and a motor, and in particular, to a control apparatus for a hybrid vehicle which controls the quantity of the increase in fuel to be supplied to the engine.
2. Description of the Related Art
Conventionally, hybrid vehicles having motors as power sources for driving the vehicles in addition to engines are known.
A parallel hybrid vehicle is a kind of hybrid vehicle that uses the motor as an auxiliary power source to supplement (assist) the output of the engine. Such a parallel hybrid vehicle performs various operations, for example, making the motor assist the output of the engine in the course of acceleration, and charging a battery by deceleration regeneration in the course of deceleration, so as to maintain sufficient remaining charge (electric energy) in the battery in order to meet demands of drivers (as disclosed, for example, in Japanese Unexamined Patent Application, First Publication, No. Hei 7-123509).
In the aforementioned conventional control apparatus for a hybrid vehicle, when a degree of throttle opening (e.g., the extent of the throttle opening) is high, controls to increase quantity of fuel supplied to an engine are carried out as in a gasoline engine vehicle so as to maintain drivability. However, the motor supplements the output of the engine in the hybrid vehicle, and within a range in which the engine speed is a predetermined value or less, while it is possible to secure adequate drivability with the assistance of the output of the engine by the motor, this may cause the problem that fuel consumption deteriorates due to an excessive increase in the amount of fuel.
It is therefore an object of the present invention to provide a control apparatus for a hybrid vehicle which prohibits the increase in the amount of fuel supplied to the engine within a range in which the engine speed is a predetermined value or less, and thereby drivability can be guaranteed and fuel consumption can be improved.
In order to accomplish the object, the first aspect of the present invention provides a control apparatus (in the embodiment described hereinafter, control apparatus 1) for a hybrid vehicle which is provided with an engine (engine E) which outputs the driving force of the vehicle (hybrid vehicle 10); a motor (motor M) which assists the output of the engine in accordance with the operational state of the vehicle; and an electricity storage device (battery 22), which stores generated energy, when the motor is employed as a generator by the output of the engine, and regenerated energy, which is produced by the regenerative state of the motor when the vehicle decelerates, comprising: a degree of throttle opening detector (step S6) for detecting the degree of throttle opening in the engine; an engine speed detector (step S2) for detecting the speed of the engine; a degree of throttle opening setting device for fuel amount increase determination (step S103) for setting a degree of throttle opening for fuel amount increase determination, which is used to determine whether the amount of fuel supplied to the engine should be increased, according to the engine speed; and a fuel amount increase prohibiting device (steps S104, S110, and S113 to S115) for prohibiting an increase in the amount of fuel supplied to the engine, when the degree of throttle opening detector detects that the degree of throttle opening is equal to or above the degree of throttle opening for fuel amount increase determination and the engine speed detector detects that the engine speed is equal to or below a predetermined engine speed.
According to the above-mentioned structure, in the region in which the engine speed is equal to or below a predetermined value, the assistance of the output of the engine by the motor makes it possible to provide good drivability, and prohibiting an increase in the amount of fuel supplied to the engine provides reduced fuel consumption.
The second aspect of the present invention provides a control apparatus for a hybrid vehicle in accordance with the first aspect of the present invention, further comprising: a remaining charge calculator (battery ECU 13) for calculating the remaining charge in the electricity storage device, wherein, when the remaining charge calculated by the remaining charge calculator is equal to or above a predetermined remaining charge, the fuel amount increase prohibiting device prohibits to increase the amount of fuel supplied to the engine (steps S106 and S107).
According to the above-mentioned structure, when it is determined that the remaining charge in the electricity storage device is equal to or above a predetermined value in the region in which the engine speed is equal to or below a predetermined value, the assistance of the output of the engine by the motor makes it possible to provide good drivability, and prohibiting the increase in the amount of fuel supplied to the engine provides reduced fuel consumption.
In a third aspect of the present invention, a control apparatus for a hybrid vehicle in accordance with the first aspect of the present invention, further comprising: a time measuring device (steps S105 and S112) for measuring the duration of the state in which the degree of throttle opening detector detects that the degree of throttle opening is equal to or larger than the degree of throttle opening for fuel amount increase determination; and a fuel amount increasing device (steps S108 to S110) for prohibiting the operation of the fuel amount increase prohibiting device so as to increase the amount of fuel supplied to the engine, when the duration measured by the time measuring device is equal to or larger than a predetermined time.
According to the above-mentioned structure, when the state in which the degree of throttle opening is high continues for a predetermined time or more, it is determined that the driver is requesting an increase in the output, then the amount of fuel supplied to the engine is increased so as to respond to the will of the driver and provide good drivability.
In a fourth aspect of the present invention, a control apparatus for a hybrid vehicle in accordance with the first aspect of the present invention, further comprising: a fuel amount increasing device (steps S108, S109, and S111) for measuring the delay of the ignition timing in the engine, and for prohibiting the operation of the fuel amount increase prohibiting device so as to increase the amount of fuel supplied to the engine, when the delay of the ignition timing in the engine is above a predetermined time.
According to the above-mentioned structure, even if there is a possibility that the use of inferior gasoline as fuel degrades the exhaust system, the amount of fuel supplied to the engine is increased, and the exhaust system can be protected.
In a fifth aspect of the present invention, a control apparatus (control apparatus 1) for a hybrid vehicle which is provided with an engine (engine E) which outputs the driving force of the vehicle (hybrid vehicle 10); a motor (motor M) which assists the output of the engine in accordance with the operational state of the vehicle; and an electricity storage device (battery 22), which stores generated energy, when the motor is employed as a generator by the output of the engine, and regenerated energy, which is produced by the regenerative state of the motor when the vehicle decelerates, comprising: a degree of throttle opening detector (step S6) for detecting the degree of throttle opening in the engine; a remaining charge calculator (battery ECU 13) for calculating the remaining charge in the electricity storage device; an engine speed detector (step S2) for detecting the speed of the engine; a degree of throttle opening setting device for fuel amount increase determination (step S203) for setting a degree of throttle opening for fuel amount increase determination, which is used to determine whether the amount of fuel supplied to the engine should be increased, according to the engine speed for each one of a plurality of predetermined values of the remaining charge; a degree of throttle opening change calculator (step S204) for calculating the amount of the change in the degree of throttle opening for fuel amount increase determination with respect to the value of the remaining charge; a degree of throttle opening correction device for fuel amount increase determination (step S204) for correcting the degree of throttle opening for fuel amount increase determination with respect to the value of the remaining charge in accordance with the degree of throttle opening change calculator; a time measuring device (steps S205 to S207) for measuring the duration of the state in which it is detected that the degree of throttle opening detected by the degree of throttle opening detector is equal to or above the degree of throttle opening for fuel amount increase determination that is corrected by the degree of throttle opening correction device for fuel amount increase determination; and a fuel amount increasing device (steps S208 and S209) for increasing the amount of fuel supplied to the engine, when the duration measured by the time measuring device is equal to or above a predetermined time.
According to the above-mentioned structure, the degree of throttle opening of the fuel amount increase determination for determining whether to increase the amount of fuel is made variable, depending on the remaining charge in the electricity storage device. Accordingly, when there is little remaining charge, by setting the degree of throttle opening of the fuel amount increase determination to a relatively low value, even if the amount of the increase in the degree of throttle opening is small, the increase in the amount of fuel can be carried out at an early stage, to provide good drivability. In contrast, when there is much remaining charge, by setting the degree of throttle opening of the fuel amount increase determination to a relatively high value, the increase in the amount of fuel is prohibited until an increase of the output is strongly demanded, so that the fuel consumption ratio can further be improved.